The phases of the Moon are the different ways the Moon looks from Earth over about a month. The phases of the Moon depend on its position in relation to the Sun and Earth. The different shapes of the lit portion of the Moon that can be seen from Earth are known as phases of the Moon. Each phase repeats itself every 29.5 days.
- When the moon is between the earth and the sun, the position is called the New Moon. It is the 1st primary phase. On New Moon, part of the moon facing the Earth is in complete darkness that’s why a New Moon cannot normally be seen from Earth.
- The moment a thin sliver of the Moon becomes visible after New Moon is the beginning of the first intermediate phase, the Waxing Crescent Moon.
- First Quarter Moon is the 2nd primary Moon phase and it is defined as the moment the Moon has reached the 1st quarter of its orbit around Earth, hence the name. It is also called Half Moon as we can see exactly 50% of the Moon's surface illuminated. Whether you see the left or right half illuminated depends on several factors, including your location.
- A waxing gibbous moon occurs when more than half of the lit portion of the Moon can be seen and the shape increases ("waxes") in size from one day to the next. The waxing gibbous phase occurs between the first quarter and full moon phases.
- A full moon is when we can see the entire lit portion of the Moon. The full moon phase occurs when the Moon is on the opposite side of the Earth from the Sun, called opposition.
- The next intermediate Moon phase is the Waning Gibbous Moon. The portion of the visible half of the Moon illuminated decreases during this period.
- The last quarter moon (or a half moon) is when half of the lit portion of the Moon is visible after the waning gibbous phase.
- A waning crescent moon is when the Moon looks like the crescent and the crescent decreases ("wanes") in size from one day to the next.